Electron discharge device utilizing cavity resonators



July 20, 1948. s. T. MARTIN, JR 2,445,447

ELECTRON DISCHARGE ICE UTILIZING CAVITY RESO CR5 2 Sheets-Sheet 1 FiledFeb. 6, 1945 ISmaentor (Ittorneg July 20, 1948. s. r. MARTIN, JR2,445,447

ELECTRON DISCHARGE DEVICE UTILIZING I I CAVITY RESONATORS Filed Feb. 6,194:5 2 Sheets-Sheet 2 ZSnnentor attorney patented July 20, 1948 UNITEDSTATES PATENT OFFICE ELECTRON DISCHARGE DEVICE UTILIZING CAVITYRESONATOR-S of Delaware Application February 6, 1943, Serial No. 474,912

9 Claims. 1

My invention relates to electron discharge devices useful at ultra highfrequencies, more particularly to such devices of the magnetron type. 1

In one form of magnetron particularlyuseful at ultra high frequencies,an elongated cathode is surrounded by a cylindrical block of conductingmaterial, for example copper, having an opening extending longitudinallytherethrough to form a .cylindrical chamber coaxial with the cathode.symmetrically spaced around the cylindrical chamber and extendinglongitudinally of the solid conducting block and parallel to the chamberare a plurality of cylindrical cavities connected with the centralchamber by means of radial slots. The result is a plurality of anodesegments connected by means of what are in effect resonant cavitycircuits. Cupshaped depressions are formed in the top and bottom ends ofthe block and the ends of the block are closed and sealed withconducting discs. The cathode leads and coupling loop are properlysealed in the block tooprovide a vacuum-tight interior. Cooling fins aresecured-to the outside of the block. There is thus provided in effect aclosed conducting envelopefor the magnetron.

In tubes of this type aproblem is presented in connection with thegettering of the tube. Conventional high frequency flashing of thegetter is not possible due to shielding of the metal envelope. Either anextra lead must be provided in the anode block or a bulb containing thegetter must be attached to one of the cathode leadcap seals. In thefirst case the extra lead makes the attachment of the cooling fins morecomplex and in the second case the position of the getter bulb greatlyincreases the hazards of destruction of the tube during handling andinstallation.

An object of my invention is to provide an electron discharge device ofthe magnetron type with an improved means of gettering the tube.

More specifically an object of my invention is to provide such a devicewhich is completely enclosed by a metal envelopebut in which the gettermay be flashed without the use of external leads for the getter, or theuse of an extra getter bulb.

The novel features which I believe to be characteristic of my inventionare set forth with particularity in the appended claims, but theinvention itself will best beunderstood by reference to the followingdescription taken inconnection with the accompanying drawing in whichFigure 1 is a top plan view with cover removed of an electron dischargedevice-made according to myiinvention, Figure 2 is a side view withparts broken away to show details of construction, Figure 3 is a planview with cover'removed of a modification of an electron dischargedevice made according to my invention, Figures 4 and 5 are partialperspectives showing details of construction of the getter arrangementsused in the electron discharge devices shownin Figures 1 to 3 inclusiveand made according to my invention.

In Figure 1 an electron discharge device of the magnetron type comprisesan indirectly heated cathode it supported by lead and support wires ll.Surrounding and coaxial with the cathode is a cylindrical anode block I2of conducting material, for example of copper, and provided at itscenter with a cylindrical chamber I3 co: axial with and surrounding thecathode. Symmetrically spaced around this cylindrical chamber l3 are aplurality of small cylindrical cavities l4, coextensive with chamber I3.The cavities are connected to the cylindrical chamber [3 by means ofradial slots [5, thus providing a plurality of anode segments betweenadjacent pairs of slots. The chambers [4 provide in effect resonantcavity circuits connected between adjacent anode segments. Thes cavitycircuits are excited during operation so that an electromagnetic fieldis generated within the cavity, the cavities being coupled with eachother by these fields. The anode block I2 is provided at its ends withcupshaped depressions I6 and 11 into which the ends of the cathode I0extend. The ends of the anode block are closed by conducting discs l8and I9 sealed with a vacuum-tight seal to the block. Cooling fins 20 aresecured to the outside of the anode block.

The cathode leads and supports l l are provided with extensions 22extending through passageways (not shown) and the tubular members 23coaxial with leads 22. A vacuum-tight seal is provided by means of theelongated cup-shaped sealing members 23.. If desired, coaxial linecables may be connected to these cathode leads for tuning the same toprevent high frequency losses in the cathode leads. A coupling loop 2,4is mounted within one of the resonant cavities, is provided with a lead25 extending through a passageway (not shown), and is surrounded by acoaxial threaded member 21 and a cup-shaped sealing member of insulatingmaterial 26. This coupling loop may be connected to a coaxialline cable,the outer line being secured to threaded member 21 and the innerconductor to the lead 25.

In accordance with my invention I position a getter loop 30 between apair of resonant cavities and connect its ends near the tip of an anodesegment and to the wall of the cup-shaped depression. As shown in Figure4 this loop 30 is of U-shaped transverse section and has within it agetter material 3| of any well known kind. The ends of the loop may bewelded at points 32 and 33. In operation an R. F. field of sufiicientintensity is generated which in extending between pairs of adjacentcavities induces a high radio frequency current in loop 39, heating thesame to flash the getter. of the magnetic field may be increased to burnthe loop out so that it will not thereafter affect the tubes operation.

A modification of my invention is shown in Figure 3. Like numbersdesignate like elements as in Figure 1.

In this modification the getter loop 35 takes the form of a closed ringas shown in Figures 3 and 5. This also may have a U-shaped transversesection and be filled with getter material 36. An arm 31 welded to thewall of the anode block positions and supports the ring above the end ofand coaxial with one of the resonant cavities. The getter may be flashedand the ring burned out in a manner similar to that shown in themodification shown in Figures 1 to 3, inclusive, by the linkage of thefield generated within the cavity and extending between cavities.

Thus with my invention, the necessity for external connections for thegetter is eliminated, the tube construction is simplified and thehazards of breakage in handling and installation are materiallydecreased.

While I have indicated the preferred embodiments of my invention ofwhich I am now aware and have also indicated only one specificapplication for which my invention may be employed, it will be apparentthat my invention is by no means limited to the exact forms illustratedor the use indicated, but that many variations may be made in theparticular structure used and the purpose for which it is employedwithout departing from the scope of my invention as set forth in theappended claims.

What I claim as new is:

1. An electron discharge device having a cathode for supplyingelectrons, an anode member of solid conducting material having a chambercentrally thereof into which electrons are directed, said anode memberhaving a plurality of cavities positioned around the central chamber andcoextensive therewith and having slots connecting said cavities withsaid central chamber to provide anode segments between said slots, and agetter loop adjacent one end of said anode member and positioned to bein the radio frequency field extending between the ends of said cavitiesfor. flashing the getter when said device is excited.

2. An electron discharge device having a cathode for supplyingelectrons, an anode member of solid conducting material having acentrally positioned chamber into which electrons are directed from saidcathode, said :anode member having a plurality of cylindrically shapedcavities positioned around said centrally positioned chamber andcoextensive therewith and having slots connecting said cavities withsaid centrally positioned chamber to provide anode segments between saidslots, and a getter loop adjacent one end of said anode member andpositioned to be in the radio frequency field extending between theAfter flashing the intensity- .ends of said cavities for flashing thegetter when said device is excited, and means for providing a magneticfield longitudinally of said centrally positioned chamber.

3. An electron discharge device having an elongated cathode, an anodeblock of cylindrical shape surrounding said cathode and provided with acentral cylindrical chamber extending longitudinally of said anodeblock, and having a plurality of cylindrically shaped cavities extendinglongitudinally of and parallel to said chamber, said block having radialslots connecting said cavities with the central chamber to provide anodesegments between said slots and cavity resonators between said segments,a getter loop positioned between adjacent cylindrically shaped cavityresonators and having one end connected near the edge of an anodesegment and its other end connected to the wall of the anode block, saidgetter loop being positioned to be in the radio frequency fieldextending between the ends Of said cavity resonators for flashing thegetter when said device is excited.

4. An electron discharge device having an elongated cathode, an anodeblock of cylindrical shape surrounding said cathode and provided with acentral cylindrical chamber extending longitudinally of said anodeblock, said anode block having a plurality of cylindrically shapedcavities extending longitudinally of and parallel to said centralchamber, said block having radial slots connecting said cavities withthe central cylindrical chamber to provide anode segments between saidslots and cavity resonators between said segments, one end of said anodeblock being provided-with a cup-shaped depression and a getter loopwithin said cupshaped depression and positioned to be in the radiofrequency field extending between the ends of said cavities for flashingthe getter when the device is excited and a conducting plate memberclosing said cup-shaped depression.

5. An electron discharge device having an elongated cathode, an anodeblock of cylindrical shape surrounding said cathode and provided with acentral cylindrical chamber extending longitudinally of said anodeblock, said block having a plurality of cylindrically shaped cavitiesextending longitudinally of and parallel to said central chamber, saidblock having radial slots connecting said cavities with the centralcylindrical chamber to provide anode segments between said slots andcavity resonators between said segments, the ends of said anode blockbeing provided with cup-shaped depressions and a getter loop positionedwithin one of said depressions, anda pair. of' conducting plate membersclosing said cup-shaped depressions, said getter loop being closed andextending from the wall of the cup-shaped depression and coaxial withone of said cavities.

6. An electron discharge device having a cathode for supplyingelectrons, a plurality of anode segments defining a space into whichsaid electrons are directed, conducting members connecting adjacentsegments and providing cavity resonators therebetween, and a getter loopadjacent one end of said anode segments and positioned to be in theradio frequency field extending between the ends of said cavityresonators for fiashing said getter when said device is excited.

7. An electron discharge device having an elongated cathode forsupplying electrons and a plurality of anode segments surrounding saidcathode, and conducting means connected between adjacent segments forproviding cavity resonators between said segments, and other metallicmeans closing the ends of said cavity resonators and enclosing saidcathode, and a getter loop adjacent one end of said anode segments andpositioned within said metallic closing means and positioned to be inthe radio frequency field extending between the ends of said cavityresonators for flashing the getter when said electron discharge deviceis excited.

8. An electron discharge device having a cathode for supplyingelectrons, an anode block of cylindrical shape surrounding a space intowhich electrons are directed from said cathode and provided with acentral cylindrical chamber extending longitudinally of said anodeblock, and having, a plurality of cylindrically shaped cavitiesextending longitudinally of and parallel to said chamber, said blockhaving radial slots connecting said cavities with the centralcylindrical chamber to provide anode segments between said slots andcavity resonators between said segments, a getter loop comprising a ringpositioned adjacent one end of said block and coaxial with one of saidcylindrically shaped cavities, said ring being secured to the wall ofthe anode block, said getter loop being positioned to be in the radiofrequency field extending between the ends of said cavity resonators forflashing the getter when said device is excited.

9. An electron discharge device having an elongated cathode and an anodeblock of cylindrical shape surrounding said cathode and provided with acentral cylindrical chamber extending longitudinally of said anodeblock, said block having a plurality of cavities extending 6longitudinally of and parallel to said chamber, said block having slotsconnecting said cavities with said central cylindrical chamber toprovide anode segments between said slots and cavity resonators betweensaid segments, the ends of said anode block being provided withcup-shaped depressions and a getter loop positioned within one of saiddepressions, and conducting plate members closing the ends of said 10anode block, said getter loop comprising a ring supported in a planetransverse to the longitudinal axis of a resonator, said ring beingcoaxial with a resonator, said getter loop being positioned to be in theradio frequency field extending between the ends of said cavityresonators for flashing the getter when said device is excited.

STUART T. MARTIN, JR.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,638,551 Rionci Aug. 9, 19272,063,342 Samuel Dec. 8, 1936 2,226,653 Allerding et al. Dec. 31, 19402,247,077 Blewett et al. June 24, 1941 2,252,118 Dallenbach et al. Aug.12, 1941 2,394,396 Mouromtseff et al. Feb. 5, 1946 2,408,234 SpencerSept. 24, 1946 2,412,302 Spencer Dec. 10, 1946 5 FOREIGN PATENTS 7Number Country Date 215,660 Switzerland Oct. 16, 1941 509,102 GreatBritain July 11, 1939

